Control Circuit for Fan

1. A control circuit comprising: a current sensing circuit to sense current supplied for an electronic device by a power supply, and output a first voltage signal; an amplifying circuit; an analog to digital converter (ADC), wherein the amplifying circuit is connected between the current sensing circuit and the ADC to amplify the first voltage signal output from the current sensing circuit to a second voltage signal, the ADC converts the second voltage signal to a digital signal; a processor to output pulse width modulation (PWM) signals according to the digital signal; and a switching circuit connected between the processor and a fan to control the fan of the electronic device according to the PWM signals; wherein the switching circuit comprises a field effect transistor (FET) and a bipolar junction transistor (BJT) transistor, a gate of the FET is connected to the processor through a first resistor, a source of the FET is grounded, a drain of the FET is connected to the power supply through a second resistor, the drain of the FET is further connected to a base of the BJT transistor through a third resistor, an emitter of the BJT transistor is connected to the power supply, a collector of the BJT transistor is connected to the fan.

2. The control circuit of claim 1 , wherein the current sensing circuit comprises a sense resistor.

3. The control circuit of claim 1 , wherein the amplifying circuit comprises a first resistor, a second resistor, and an amplifier, a first terminal of the first resistor is connected to a first output terminal of the current sensing circuit, a second terminal of the first resistor is connected to an inverting terminal of the amplifier, the inverting terminal of the amplifier is further connected to an output terminal of the amplifier, a non-inverting terminal of the amplifier is connected to a second output terminal of the current sensing circuit, the output terminal of the amplifier is further connected to the ADC.

4. A control circuit comprising: a current sensing circuit to sense current supplied for an electronic device by a power supply and output a voltage signal correspondingly; an analog to digital converter (ADC) to convert the voltage signal to a digital signal; a processor to output pulse width modulation (PWM) signals according to the digital signal; and a switching circuit connected between the processor and a fan to control the fan of the electronic device according to the PWM signals; wherein the switching circuit comprises a field effect transistor (FET) and a bipolar junction transistor (BJT) transistor, a gate of the FET is connected to the processor through a first resistor, a source of the FET is grounded, a drain of the FET is connected to the power supply through a second resistor, the drain of the FET is further connected to a base of the BJT transistor through a third resistor, an emitter of the BJT transistor is connected to the power supply, a collector of the BJT transistor is connected to the fan.

5. The control circuit of claim 4 , wherein the current sensing circuit comprises a sense resistor.